Autoregulation of renal blood flow and the glomerular filtration rate will be studied in isolated kidneys. Factors to be assessed include intrarenal hormones, distribution of intrarenal blood flow, physical and oncotic influences, vasodilators, tubular and renal pressures, and salt and water excretion. The mode of action of diuretics and effects on renal metabolism will be measured in isolated kidneys. Factors which affect renal vascular reactivity and responses to vasoactive compounds will be investigated in this same preparation.